Under this continuation of HD22433, we will use the second wave of the National Survey of Families and Households to extend our research on union formation and dissolution with an explicit focus on the implications of cohabitation for family boundaries and for our conceptual and analytic family nomenclature. Among the major advantages of this data set are: l) The depth of the 1987-88 (T1) measures on family attitudes and behaviors; 2) Data from both males and females; and 3) Data from both partners for the analysis of marriage among cohabiters and union disruption among both cohabiting and married couples. We have four specific aims. 1) The Formation of Unions Among Unmarried Persons at T1: For noncohabiting persons, transitions to first cohabitation or first marriage will be examined in relation to T1 attitudes towards cohabitation and marriage, background, resources, and life-course variables including measures of T1 dating behavior. For cohabiters, transitions to marriage will be examined in the above framework adding relationship quality. Transitions to marriage will then examined for all unmarried. 2) All Cohabitation and Marriage Transitions Between Interviews: Educational, and employment changes between interviews will be added as time-varying covariates to predict cohabitation from not being in a union and marriage from both cohabitation and not-in-union. 3) Non marital Childbearing in the Context of Cohabitation and Marriage Timing: including cohabitation as a time-varying covariate, we will examine how background factors and T1 resources (such as education and income) affect the risk of a nonmarital birth through T1 attitudes and cohabitation and marriage patterns. The inclusion of standard measures of fertility planning in NSFH2 will allow us to differentiate between planned and unplanned births in this analysis. 4) Cohabitation and Union Stability: First, the higher disruption rate of marriages preceded by cohabitation will be examined by models including measures of relationship quality and orientations towards marriage and divorce. Second, using comparable measures on relationship quality drawn from both partners, the stability of cohabiting and married couples of similar durations will be examined.